1. Field of the Invention
This invention relates to computer systems, and more particularly to functionally redundant computer systems as well as their use in a testing environment.
2. Description of the Related Art
Functionally redundant computer systems are well known in the art, and have a wide variety of applications. Functional redundancy may be implemented in computer systems requiring a high degree of reliability, such as in fault tolerant computer systems. A fault tolerant computer system utilizing functional redundancy typically includes two or more processors. The processors operate in synchronous functional lockstep with each other, i.e. each processor concurrently receives the same inputs, and is expected to concurrently provide the same outputs. Comparators (sometimes referred to as voting circuits) compare outputs from the processors. The comparator can detect a mismatch between the outputs of the two or more processors, and, depending on the configuration of the system, determine which of the processors has provided the correct output.
Functionally redundant computer systems such as those described above may also be useful in a test environment. For example, a system for testing a processor may be designed where a processor is tested by comparing its responses with those of a known good processor. A detected mismatch between processor outputs may indicate a fault in the processor that is undergoing test. The test system may also be configured to capture the state data at the time of the failure, which, at times may be useful in determining its cause. Test systems utilizing functional redundancy may be useful in both development and manufacturing environments.